Electroencephalography (EEG) is the recording of electrical activity exhibited by the brain using electrodes positioned on a subject's scalp, forming a spectral content of neural signal oscillations that comprise an EEG data set. For example, the electrical activity of the brain that is detected by EEG techniques can include voltage fluctuations, e.g., resulting from ionic current flows within the neurons of the brain. In some contexts, EEG refers to the recording of the brain's spontaneous electrical activity over a short period of time, e.g., less than an hour. EEG can be used in clinical diagnostic applications including epilepsy, coma, encephalopathies, brain death, and other diseases and defects, as well as in studies of sleep and sleep disorders. In some instances, EEG has been used for the diagnosis of tumors, stroke and other focal brain disorders.
One example of an EEG technique includes recording of event-related potentials (ERPs), which refer to EEG recorded brain responses that are correlated with a given event (e.g., simple stimulation and complex processes). For example, an ERP includes an electrical brain response—a brain wave—related to the sensory, motor, and/or cognitive processing. ERPs are associated with brain measures of perception (e.g., visual, auditory, etc.) and cognition (e.g., attention, language, decision making, etc.). For example, ERPs can also be used as objective measures in the evaluation and monitoring of neurological or neuropsychiatric disorders. A typical ERP waveform includes a temporal evolution of positive and negative voltage deflections, termed components. For example, typical components are classified using a letter (N/P: negative/positive) and a number (indicating the latency, in milliseconds from the stimulus event), for which this component arises.